With the S&P 500 index tripling since March 2009, many investors have become overweighted in stocks, and that could turn into a problem for those nearing retirement, experts say.

A recent study by Fidelity Investments of its 401(k) accounts showed that 27 percent of investors in their mid- to late-50s have an equity weighting 10 percent higher than recommended.

If stocks fall, that could mean major losses for people just about to enter retirement, USA Today reports.

"That's concerning, especially at that age,'' Jeanne Thompson, vice president at Fidelity Investments, told the paper. "You want to make sure you have a little more balance, that you hold a little bit in bonds [and cash], so you don't lose your whole nest egg, or much of it."'

Bonds, of course, generally provide more safety. Treasurys were one of the few asset classes to rise during the financial crisis of 2008-09.

USA Today's Charisse Jones recommends rebalancing your 401(k) plan at least once a year if your stock weighting is at least 10 percent higher than your goal.

Elsewhere on the retirement front, a recent American Enterprise Institute forum addressed an important issue, says Steve Vernon a research scholar for the Stanford Center on Longevity: have we got a crisis, or merely a series of hard problems?

The news media is full of reports that we are woefully unprepared financially for retirement. But panelists said that some of these reports have overstated the difficulties.

"Is it really a crisis if people who are fully capable of working must continue to work in their late 60s or early 70s to make ends meet?" Vernon writes in a column on CBS Moneywatch.

"Or if they must wait to start Social Security benefits until their late 60s or age 70? Or if they're forced to accept a reduced living standard in retirement?"

Many experts recommend raising the age requirements for Social Security and Medicare.

You can start receiving Social Security payments at 62, and you can generally join Medicare shortly before you turn 65.

Maybe the issue should be defined differently, Vernon says.

"Perhaps this situation merely represents a hard problem with unfortunate consequences, the result of a host of circumstances ranging from inadequate planning and saving for retirement to simple bad luck?"
 
Related Stories:

• Cheat Sheet's McWhinnie: How to Retire Early by Improving Finances
• Retirement Survey: Many of Us Fail to Consult Financial Advisers